A Treatise on Painting/Chapter 311
Appearance
Chap. CCCXI.—Of Buildings seen in a thick Air.
That part of a building seen through a thick air, will appear less distinct than another part seen through a thinner air. Therefore the eye, N, looking at the
tower A D, will see it more confusedly in the lower degrees, but at the same time lighter; and as it ascends to the other degrees it will appear more distinct, but somewhat darker.